Renting out the basement portion of a home has become extremely popular in the Seattle area. With Seattle’s high cost of living and high rents—and all that potential extra space not being use—it certainly makes sense. To avoid getting into some hot water, however, there are some things you need to know before placing a Craigslist ad. In order to legally rent out a basement, the rented portion of the home needs to be permitted as an accessory dwelling unit (ADU). To add an ADU to an existing house you need a construction/alteration permit. To legalize an existing unit you need a construction permit to establish use. In both cases you may also need to apply for electrical service charges or new services from Seattle City Light.

The City of Seattle lists the following as requirements for establishing an ADU:

An ADU is limited to 1,000 square feet in a single-family structure and up to 650 square feet in a rowhouse or townhouse

The ADU must meet current standards of the Seattle residential, building, mechanical, electrical, energy, land use, environmentally critical areas, and shorelines codes

One off-street parking space is required for the ADU except for a rowhouse or townhouse in designated urban villages and urban centers and in lowrise zones

Note also that City of Seattle codes require the owner to live either in the house or the ADU and even require a signed owner occupancy covenant agreeing to this condition.

In addition to codes establishing an ADU, further city codes enforce rental maintenance and rules regarding landlords’ and tenants’ rights and responsibilities. Violation of any of the above codes generally comes to the attention of the city through a complaint by tenants or neighbors and fines can be stiff. The City of Seattle website states that if you receive notice of a code violation and don’t fix the problem in a timely manner, they may fine you $150-$500 a day—so be sure to research those codes before renting out the basement!